[1] A. V. Dmitruk A. A. Miljutin, N. P. Osmolovski:
Theorem of Lusternik and Theory of Extremum. UMN 35 (1980), 11-46 (in Russian).
MR 0601755
[2] A. D. Ioffe, V. M. Tihomirov:
The Theory of Extremal Problems. Nauka, Moskow (1974) (in Russian).
MR 0410502
[3] V. Pták:
A Quantitative refinement ofthe Closed Graph Theorem. Czechoslovak Math. J. 24 (1974), 503-506.
MR 0348431
[4] V. Pták:
Nondiscrete Mathematical Induction and Iterative Existence Proofs. Linear Algebra and its Applications 13 (1976), 223-238.
MR 0394119
[5] V. Pták:
A Nonlinear Subtraction Theorem. Proc. R. Ir. Acad. Vol. 82A, No. 1, 47-53 (1982).
MR 0669466
[6] F. A. Potra, V. Pták:
Nondiscrete induction and iterative processes. Boston etc., Pitman Advanced Publishing Program, 1984.
MR 0754338